128 



Shell Life 



The general characters of the mollusks comprising 

 the sub-order Yeneracea are ' an ahnost round or 

 oblong shell of equal valves, whose hinge has three 

 diverging cardinal teeth, the muscular impressions 

 oval and polished, and the mantle impression showing 

 a deep sinus into which the siphons are retracted 

 when not in use. The animal has unequal gills 

 which are slightly folded ; the foot is large, tongue- 

 shaped, and adapted for burrowing in sand, gravel, or 

 mud, in which the sj^ecies live. The siphons are 

 unequal, cylindrical, and in general short, showing 



that the mollusk does 

 not go far below the 

 surface, and in most 

 cases t h e }^ are 

 speckled in a way 

 that makes them har- 

 monise with the sand. 

 The deep sinus of the 

 mantle-impression is 

 a character serving 

 to distinguish any member of the family from related 

 genera. A good example of the family may be found 

 in the Smooth Venus {Venus chione), whose massive 

 shell may be found after gales thrown up on sandy 

 beaches of the Cornish coast. But our enumeration 

 of the species must begin with one that is not so 

 typical, because, its tubes being so very short their 

 withdrawal has not produced a deep sinus in the 

 impression of the mantle within. 



The Little Circe-shell . (Oirce minimia) is the only 

 native representative of its genus. It has a nearly 

 round, flattened shell, with broad, flattened, plate- 



Smnoth Venus 



